WO2024073987A1

WO2024073987A1 - Method and apparatus for harq-ack feedback timing indication for sidelink transmission over unlicensed spectrum

Info

Publication number: WO2024073987A1
Application number: PCT/CN2023/073195
Authority: WO
Inventors: Haipeng Lei; Xiaodong Yu; Zhennian SUN; Xin Guo
Original assignee: Lenovo Beijing Ltd
Current assignee: Lenovo Beijing Ltd
Priority date: 2023-01-19
Filing date: 2023-01-19
Publication date: 2024-04-11
Anticipated expiration: 2025-07-19

Abstract

Embodiments of the present disclosure relate to methods and apparatuses for HARQ-ACK feedback timing indication for a sidelink transmission over an unlicensed spectrum. According to some embodiments of the disclosure, a UE may: receive, from a second UE, an SCI for scheduling a PSSCH, wherein the SCI includes an indicator for determining one or multiple PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH; determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and transmit, to the second UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions in response to a channel access procedure for transmitting the first PSFCH being successful.

Description

METHOD AND APPARATUS FOR HARQ-ACK FEEDBACK TIMING INDICATION FOR SIDELINK TRANSMISSION OVER UNLICENSED SPECTRUM

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to wireless communication technology, and more particularly to hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback timing indication for a sidelink transmission over an unlicensed spectrum.

BACKGROUND

Wireless communication systems are widely deployed to provide various telecommunication services, such as telephony, video, data, messaging, broadcasts, and so on. Wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power) . Examples of wireless communication systems may include fourth generation (4G) systems, such as long term evolution (LTE) systems, LTE-advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may also be referred to as new radio (NR) systems.

In the above wireless communication systems, a user equipment (UE) may communicate with another UE via a data path supported by an operator's network, e.g., a cellular or a Wi-Fi network infrastructure. The data path supported by the operator's network may include a base station (BS) and multiple gateways.

A wireless communication system may also support sidelink communications, in which devices (e.g., UEs) that are relatively close to each other may communicate with one another directly via a sidelink, rather than being linked through the BS. The term "sidelink" may refer to a radio link established for communicating among devices (e.g., UEs) , as opposed to communicating via the cellular infrastructure (e.g., uplink and downlink) . Sidelink transmission may be performed on a licensed spectrum and/or an unlicensed spectrum.

There is a need for handling sidelink transmissions on an unlicensed spectrum.

SUMMARY

Some embodiments of the present disclosure provide a first user equipment (UE) . The first UE may include a transceiver, and a processor coupled to the transceiver. The processor may be configured to: receive, from a second UE, sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH) , wherein the SCI includes an indicator for determining one or multiple physical sidelink feedback channel (PSFCH) transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH; receive, from the second UE, the PSSCH on an interlace; determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and transmit, to the second UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions in response to a channel access procedure for transmitting the first PSFCH being successful.

In some embodiments of the present disclosure, the indicator indicates a first offset value of a plurality of offset values from a HARQ-ACK feedback timing set. The first offset value indicates an offset between a slot where the PSSCH is received to a slot where the first PSFCH is transmitted.

In some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, each of which indicates an offset between a slot where the PSSCH is received and a slot where a corresponding PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted.

In some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, which includes a second offset value indicating an offset between a slot where the PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted. Each of the remaining offset values of the one or multiple offset values indicates a slot level offset between an associated PSFCH transmission occasion and its preceding PSFCH transmission occasion of the one or multiple PSFCH transmission occasions.

In some embodiments of the present disclosure, the HARQ-ACK feedback timing set is configured by a base station (BS) or the second UE.

In some embodiments of the present disclosure, the processor is further configured to drop subsequent PSFCH transmission occasion (s) of the one or multiple PSFCH transmission occasions in response to transmitting the first PSFCH in the first PSFCH transmission occasion.

Some embodiments of the present disclosure provide a second user equipment (UE) . The second UE may include a transceiver, and a processor coupled to the transceiver. The processor may be configured to: transmit, to a first UE, an SCI for scheduling a PSSCH, wherein the SCI includes an indicator for the first UE to determine one or multiple PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH; transmit, to the first UE, the PSSCH on an interlace; determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and receive, from the first UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions.

In some embodiments of the present disclosure, the indicator indicates a first offset value of a plurality of offset values from a HARQ-ACK feedback timing set. The first offset value indicates an offset between a slot where the PSSCH is transmitted and a slot where the first PSFCH is received.

In some embodiments of the present disclosure, the first PSFCH resource is determined based on the index of the interlace, the first offset value, and a number of values in the plurality of offset values.

In some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, each of which indicates an offset between a slot where the PSSCH is transmitted and a slot where a corresponding PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is received.

In some embodiments of the present disclosure, determining a PSFCH resource for each of the one or multiple PSFCH transmission occasions includes: for each of the one or multiple PSFCH transmission occasions, determining a PSFCH resource based on the index of the interlace, a corresponding offset value in the first subset, and a number of subsets of the plurality of subsets.

In some embodiments of the present disclosure, a number of the one or multiple PSFCH transmission occasions is based on a number of offset values in the first subset.

In some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, which includes a second offset value indicating an offset between a slot where the PSSCH is transmitted and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is received.

In some embodiments of the present disclosure, each of the remaining offset values of the one or multiple offset values indicates a slot level offset between an associated PSFCH transmission occasion and its preceding PSFCH transmission occasion of the one or multiple PSFCH transmission occasions.

In some embodiments of the present disclosure, determining a PSFCH resource for each of the one or multiple PSFCH transmission occasions includes: for each of the one or multiple PSFCH transmission occasions, determining a PSFCH resource based on the index of the interlace, offset values associated with a PSFCH transmission occasion and its preceding PSFCH transmission occasion (s) among the one or multiple offset values, and a number of subsets of the plurality of subsets.

In some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes a third offset value indicating an offset between a slot where the PSSCH is transmitted and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is received, or both the third offset value and HARQ-ACK feedback transmission times.

In some embodiments of the present disclosure, in the case that the first subset does not include the HARQ-ACK feedback transmission times, a number of the one or multiple PSFCH transmission occasions is equal to 1. In some embodiments of the present disclosure, in the case that the first subset includes the HARQ-ACK feedback transmission times, the number of the one or multiple PSFCH transmission occasions is equal to the HARQ-ACK feedback transmission times.

In some embodiments of the present disclosure, the first subset further indicates a slot level offset between two adjacent PSFCH transmission occasions of the one or multiple PSFCH transmission occasions. In some embodiments of the present disclosure, the slot level offset is configured by a BS or the second UE. In some embodiments of the present disclosure, the slot level offset is predefined.

In some embodiments of the present disclosure, determining a PSFCH resource for each of the one or multiple PSFCH transmission occasions includes: for each of the one or multiple PSFCH transmission occasions, determining a PSFCH resource based on the index of the interlace, the third offset value, the slot level offset and a number of subsets of the plurality of subsets.

In some embodiments of the present disclosure, the HARQ-ACK feedback timing set includes an inapplicable offset value for disabling HARQ-ACK feedback for a PSSCH.

In some embodiments of the present disclosure, the HARQ-ACK feedback timing set is configured by a BS or the second UE.

Some embodiments of the present disclosure provide a method performed by a first UE. The method may include: receiving, from a second UE, an SCI for scheduling a PSSCH, wherein the SCI includes an indicator for determining one or multiple PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH; receiving, from the second UE, the PSSCH on an interlace; determining, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and transmitting, to the second UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions in response to a channel access procedure for transmitting the first PSFCH being successful.

Some embodiments of the present disclosure provide a method performed by a second UE. The method may include: transmitting, to a first UE, an SCI for scheduling a PSSCH, wherein the SCI includes an indicator for the first UE to determine one or multiple PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH; transmitting, to the first UE, the PSSCH on an interlace; determining, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and receiving, from the first UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions.

Some embodiments of the present disclosure provide an apparatus. According to some embodiments of the present disclosure, the apparatus may include: at least one non-transitory computer-readable medium having stored thereon computer-executable instructions; at least one receiving circuitry; at least one transmitting circuitry; and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuitry and the at least one transmitting circuitry, wherein the at least one non-transitory computer-readable medium and the computer executable instructions may be configured to, with the at least one processor, cause the apparatus to perform a method according to some embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the advantages and features of the disclosure can be obtained, a description of the disclosure is rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. These drawings depict only exemplary embodiments of the disclosure and are not therefore to be considered limiting of its scope.

FIG. 1 illustrates a schematic diagram of a wireless communication system in accordance with some embodiments of the present disclosure;

FIG. 2 illustrates an example of an interlace-based resource block configuration in accordance with some embodiments of the present disclosure;

FIGS. 3 and 4 illustrate examples of HARQ-ACK feedback timing determination in accordance with some embodiments of the present disclosure;

FIGS. 5 and 6 illustrate flow charts of exemplary procedures of sidelink communications in accordance with some embodiments of the present disclosure; and

FIG. 7 illustrates a block diagram of an exemplary apparatus in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The detailed description of the appended drawings is intended as a description of the preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure may be practiced. It should be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present disclosure.

Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under a specific network architecture (s) and new service scenarios, such as the 3rd generation partnership project (3GPP) 5G (NR) , 3GPP long-term evolution (LTE) Release 8, and so on. It is contemplated that along with the developments of network architectures and new service scenarios, all embodiments in the present disclosure are also applicable to similar technical problems; and moreover, the terminologies recited in the present disclosure may change, which should not affect the principles of the present disclosure.

FIG. 1 illustrates a schematic diagram of a wireless communication system 100 in accordance with some embodiments of the present disclosure.

As shown in FIG. 1, wireless communication system 100 may include a base station (e.g., BS 120) and some UEs 110 (e.g., UE 110a, UE 110b, and UE 110c) . Although a specific number of UEs 110 and one BS 120 are depicted in FIG. 1, it is contemplated that any number of BSs and UEs in and outside of the coverage of the BSs may be included in the wireless communication system 100.

In some embodiments of the present disclosure, BS 120 may be referred to as an access point, an access terminal, a base, a base unit, a macro cell, a Node-B, an evolved Node B (eNB) , a gNB, a Home Node-B, a relay node, or a device, or described using other terminology used in the art. BS 120 is generally a part of a radio access network that may include one or more controllers communicably coupled to one or more corresponding BSs. BS 120 may communicate with UE (s) 110 via downlink (DL) communication signals.

UE (s) 110 (e.g., UE 110a, UE 110b, or UE 110c) may include computing devices, such as desktop computers, laptop computers, personal digital assistants (PDAs) , tablet computers, smart televisions (e.g., televisions connected to the Internet) , set-top boxes, game consoles, security systems (including security cameras) , vehicle on-board computers, network devices (e.g., routers, switches, and modems) , or the like. According to some embodiments of the present disclosure, UE (s) 110 may include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiver, or any other device that is capable of sending and receiving communication signals on a wireless network. In some embodiments of the present disclosure, UE (s) 110 includes wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, UE (s) 110 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, an IoT device, a vehicle, or a device, or described using other terminology used in the art. UE (s) 110 may communicate with BS 120 via uplink (UL) communication signals.

Wireless communication system 100 may be compatible with any type of network that is capable of sending and receiving wireless communication signals. For example, wireless communication system 100 is compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA) -based network, a code division multiple access (CDMA) -based network, an orthogonal frequency division multiple access (OFDMA) -based network, an LTE network, a 3GPP-based network, a 3GPP 5G network, a satellite communications network, a high altitude platform network, and/or other communications networks.

In some embodiments of the present disclosure, wireless communication system 100 is compatible with 5G NR of the 3GPP protocol. For example, BS 120 may transmit data using an orthogonal frequency division multiple (OFDM) modulation scheme on the DL and UE (s) 110 may transmit data on the UL using a discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix-OFDM (CP-OFDM) scheme. More generally, however, the wireless communication system 100 may implement some other open or proprietary communication protocols, for example, WiMAX, among other protocols.

In some embodiments of the present disclosure, BS 120 and UE (s) 110 may communicate using other communication protocols, such as the IEEE 802.11 family of wireless communication protocols. Further, in some embodiments of the present disclosure, BS 120 and UE (s) 110 may communicate over licensed spectrums, whereas in some other embodiments, BS 120 and UE (s) 110 may communicate over unlicensed spectrums. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol.

BS 120 may define one or more cells, and each cell may have a coverage area 130. In the exemplary wireless communication system 100, some UEs (e.g., UE 110a and UE 110b) are within the coverage of BS 120, which may not be the specific BS 120 as shown in FIG. 1 and can be any one of the BSs 120 in a wireless communication system, and some UEs (e.g., UE 110c) are outside of the coverage of BS 120. For example, in the case that the wireless communication system includes two BSs 120 with UE 110a being within the coverage of any one of the two BSs means that UE 110a is within the coverage of a BS 120 (i.e., in-coverage) in the wireless communication system; and UE 110a being outside of the coverage of both BSs 120 means that UE 110a is outside the coverage of a BS 120 (i.e., out-of-coverage) in the wireless communication system.

Still referring to FIG. 1, UE 110a and UE 110b may communicate with BS 120 via, for example, a Uu link (denoted by dotted arrow in FIG. 1) . UE 110a, UE 110b, and UE 110c may communicate with each other via a sidelink (denoted by solid arrow in FIG. 1) .

Sidelink transmission may involve a physical sidelink control channel (PSCCH) and an associated physical sidelink shared channel (PSSCH) , which is scheduled by the sidelink control information (SCI) carried on the PSCCH. The SCI and associated PSSCH may be transmitted from a transmitting UE (hereinafter referred to as "Tx UE" ) to a receiving UE (hereinafter referred to as "Rx UE" ) in a unicast manner, to a group of Rx UEs in a groupcast manner, or to Rx UEs within a range in a broadcast manner. For example, referring to FIG. 1, UE 110a (acting as a Tx UE) may transmit data to UE 110b or UE 110c (acting as an Rx UE) .

The PSSCH may carry data which may require corresponding HARQ-ACK feedback from the Rx UE (s) to the Tx UE. In some embodiments, broadcast transmission may not need HARQ-ACK feedback. In some embodiments, unicast and groupcast transmission may enable HARQ-ACK feedback under some preconditions. The HARQ-ACK feedback for a PSSCH may be carried on a physical sidelink feedback channel (PSFCH) .

In some embodiments of the present disclosure, sidelink transmission may be performed on an unlicensed spectrum. This is advantageous because a sidelink transmission over an unlicensed spectrum can achieve, for example, an increased data rate (s) . In order to achieve fair coexistence between various systems, for example, NR systems (e.g., NR-U systems) and other wireless systems, a channel access procedure, also known as a listen-before-talk (LBT) test, may be performed before communicating on the unlicensed spectrum. When the LBT test is successful, a Tx UE can transmit a sidelink transmission (e.g., PSSCH) to an Rx UE and may wait for the reception of a PSFCH from the Rx UE. Otherwise, if the LBT test fails, the Tx UE cannot start any transmission on the channel, and may continue to perform another LBT test (s) until a successful LBT test result.

Similarly, an Rx UE may need to perform an LBT test before transmitting the PSFCH to the Tx UE on an unlicensed spectrum. The HARQ-ACK feedback may not be transmitted if the LBT test at the Rx UE side fails. Without such HARQ-ACK feedback, the Tx UE may have to retransmit the PSSCH even though the Rx UE has correctly decoded the PSSCH.

Furthermore, even if the LBT test at the Rx UE side is successful, and the Rx UE transmits the PSFCH to the Tx UE, the Tx UE may not correctly decode the PSFCH due to hidden node interference on the shared unlicensed spectrum. In that sense, the Tx UE may have to retransmit the PSSCH even though the Rx UE has correctly decoded the PSSCH.

Embodiments of the present disclosure provide solutions to improve the reliability of PSFCH transmission over an unlicensed spectrum, which can solve at least the above issues. For example, solutions that can solve PSFCH transmission dropping due to an LBT failure for a sidelink transmission over an unlicensed spectrum are proposed. For example, solutions for PSFCH resource determination for sidelink HARQ-ACK feedback transmissions over an unlicensed spectrum are proposed. By adopting the proposed solutions, spectrum utilization efficiency can be further increased with simple UE implementation. More details on the embodiments of the present disclosure will be illustrated in the following text in combination with the appended drawings.

For a sidelink transmission over an unlicensed spectrum, the interlace-based structure can be adopted for sidelink channels. In some embodiments, when the interlace-based structure is employed for sidelink transmissions, a PSFCH resource pool may be defined based on the interlace resources.

An interlace may be defined as a set of resource blocks (RBs) equally spaced in the frequency domain. For example, multiple interlaces of RBs may be defined in common RBs based on subcarrier spacing (SCS) . The total number of interlaces in the frequency domain may be dependent on only the SCS of a carrier, regardless of concrete carrier bandwidth. For example, for 15 kHz SCS, there may be 10 interlaces on the carrier; and for 30 kHz SCS, there may be 5 interlaces on the carrier.

The number of RBs of each interlace may be dependent on the concrete carrier bandwidth. For example, for a 20 MHz bandwidth with 15 kHz SCS, each of the 10 interlaces may include 10 or 11 RBs; and for a 20 MHz bandwidth with 30 kHz SCS, each of the 5 interlaces may include 10 or 11 RBs. For a carrier bandwidth larger than 20 MHz, the same spacing between consecutive RBs in an interlace may be maintained for all interlaces regardless of the carrier bandwidth. That is, the number of RBs per interlace may be dependent on the carrier bandwidth. Keeping the same interlace spacing with increasing bandwidth is a straightforward and simple way to scale the interlace design from 20 MHz to a wider bandwidth (s) . For example, for an 80 MHz bandwidth with 30 kHz SCS, each of the 5 interlaces may include 43 or 44 RBs.

FIG. 2 illustrates an example of interlace-based resource block configuration 200 for 15 kHz SCS according to some embodiments of the present disclosure. It should be understood that configuration 200 is only for illustrative purposes, and should not be construed as limiting the embodiments of the present disclosure.

As shown in FIG. 2, carrier bandwidth may be partitioned into RBs. For illustrative purposes, FIG. 2 only shows a part of the RBs (e.g., RBs that are represented with reference numerals 2000 to 2035 in FIG. 2) included in the carrier bandwidth. Persons skilled in the art can readily know the number of RBs included in a certain carrier bandwidth by referring to bandwidth configurations for different SCSs.

As mentioned above, the number of interlaces distributed within the bandwidth of a carrier may be based on only the SCS regardless of the bandwidth of the carrier. In the example of FIG. 2, the RBs of the carrier bandwidth are partitioned into 10 interlaces (corresponding to 15 kHz SCS) , which are represented with reference numerals 210, 211, 212, 213, 214, 215, 216, 217, 218, and 219 in FIG. 2.

Each interlace of the 10 interlaces may include evenly-spaced RBs in the frequency domain. The number of RBs included in each of the 10 interlaces may depend on carrier bandwidth. As shown in FIG. 2, interlace 210 may include RB 2000, RB 2010, RB 2020, RB 2030, and so on; interlace 211 may include RB 2001, RB 2011, RB 2021, RB 2031, and so on; and interlace 219 may include RB 2009, RB 2019, RB 2029, and so on. RB 2000 to RB 2035 may be indexed from "0" to "35" along the frequency axis, and interlaces 210 to 219 may be indexed from "0" to "9" .

In some embodiments of the present disclosure, for a sidelink transmission over an unlicensed spectrum, a HARQ-ACK feedback timing set may be configured for indicating candidate timing offsets from a PSSCH to the corresponding PSFCH. The HARQ-ACK feedback timing set may be configured by a BS, by a Tx UE for an Rx UE, or by an Rx UE for a Tx UE, or may be predefined in standards or preconfigured.

In some embodiments, the HARQ-ACK feedback timing set may include one or multiple values. Each HARQ-ACK feedback timing value corresponds to a slot level offset between the slot where a PSSCH is received (e.g., received by the Rx UE or transmitted by the Tx UE) and a slot where the corresponding PSFCH carrying the HARQ-ACK feedback (e.g., one HARQ-ACK information bit) for the PSSCH is transmitted (e.g., transmitted by the Rx UE or received by the Tx UE) . In some embodiments, the HARQ-ACK feedback timing set may include an inapplicable value (e.g., a negative value such as “-1” ) , which can be defined as indicating that the HARQ-ACK feedback is disabled. The HARQ-ACK enabling/disabling indicator (if any) in the SCI can thus be removed.

In some embodiments, an indicator (denoted as indicator #1) in the SCI may be used to indicate a specific value from the HARQ-ACK feedback timing set. The number of bits of indicator #1 can be based on the number of values in the HARQ-ACK feedback timing set. In this way, the PSFCH transmission occasion is determined based on indicator #1.

For example, it is assumed that that the HARQ-ACK feedback timing set is configured as {+2, +3, +4, +5, +6, +8, -1} . According to the above embodiments, the value “-1” in the set means that the HARQ-ACK feedback is disabled and the remaining values in the set indicate a slot level offset between the slot where a PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted.

For example, referring to FIG. 3, a UE may receive a PSSCH in slot n. In the case that indicator #1 of the SCI scheduling the PSSCH indicates the 1st value (i.e., +2) of the above HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH is to be transmitted in slot n+2 (e.g., in PSFCH resource 321) . In the case that indicator #1 of the SCI scheduling the PSSCH indicates the 3^rd value (i.e., +4) of the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH is to be transmitted in slot n+4 (e.g., in PSFCH resource 322) . In the case that indicator #1 of the SCI scheduling the PSSCH indicates the 5^th value (i.e., +6) of the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH is to be transmitted in slot n+6 (e.g., in PSFCH resource 323) . In the case that indicator #1 of the SCI scheduling the PSSCH indicates the 6^th value (i.e., +8) of the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH is to be transmitted in slot n+8 (e.g., in PSFCH resource 324) . In the case that indicator #1 of the SCI scheduling the PSSCH indicates the 7^th value (i.e., -1) of the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH is disabled.

From the perspective of an Rx UE, it may receive an SCI and a PSSCH scheduled by the SCI. The Rx UE can determine a PSFCH transmission occasion for transmitting HARQ-ACK feedback corresponding to the PSSCH based on indicator #1 in the SCI. Assuming that the PSSCH is received on an interlace (denoted as interlace #1) , the Rx UE can determine a PSFCH resource for the PSFCH transmission occasion based on interlace #1 (e.g., from a PSFCH resource pool) , indicator #1 and the HARQ-ACK feedback timing set. The Rx UE may transmit a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on the determined PSFCH resource in the PSFCH transmission occasion in response to the LBT test for transmitting the PSFCH being successful.

From the perspective of the Tx UE, it may transmit the SCI and the PSSCH scheduled by the SCI. The Tx UE can determine the PSFCH transmission occasion for transmitting HARQ-ACK feedback corresponding to the PSSCH based on indicator #1 in the SCI. The Tx UE can determine a PSFCH resource for the PSFCH transmission occasion based on interlace #1, indicator #1 and the HARQ-ACK feedback timing set. The Tx UE can detect and receive the PSFCH in the determined PSFCH resource in the determined PSFCH transmission occasion.

Various methods may be employed for determining the PSFCH resource from a PSFCH resource pool.

In some embodiments, the PSFCH resource may be determined based on the interlace where the PSSCH is received (e.g., interlace #1) , the HARQ-ACK feedback timing set (e.g., the number of values in the set) , and the indicated HARQ-ACK timing value associated with the PSSCH (e.g., indicator #1) .

For example, it is assumed that there are a total of M interlaces on the channel in the frequency domain (e.g., for 15 kHz SCS, M=10; and for 30 kHz SCS, M=5) . In some examples, the M interlaces can be indexed from 0 to M-1. A PSFCH resource pool may be defined considering the interlace resources and cyclic shift (CS) pair resources and include Y PSFCH resources. Each PSFCH resource in the pool may have an associated resource index within the PSFCH resource pool.

It is assumed that there are N values with applicable HARQ-ACK feedback timing values (e.g., non-negative integer values) in the HARQ-ACK feedback timing set. Denoting k as the HARQ-ACK timing value indicated by indicator #1 in the SCI and m as the interlace index among the M interlaces (0<=m<=M-1) , for a given PSSCH transmitted on interlace m in slot n, (or m denotes the index of a predefined interlace among multiple interlaces (e.g., the lowest interlace index) for a given PSSCH transmitted on the multiple interlaces) , the corresponding PSFCH resource index can be expressed below as one example:

where k_min denotes the minimum applicable value in the HARQ-ACK feedback timing set anddenotes the PSFCH resource index pointing to one PSFCH resource within the PSFCH resource pool. In this example, the PSFCH resource allocation starts in an ascending order of k and continues in an ascending order of m. The PSFCH resource mapping for a PSSCH is in an order of time first and frequency (interlace) second manner.

In another example, the PSFCH resource allocation starts in an ascending order of m and continues in an ascending order of k. Then the PSFCH resource mapping for a PSSCH is in an order of frequency (interlace) first and time second manner.

Alternatively, can be expressed as or where k_max denotes the maximum (applicable) value in the HARQ-ACK feedback timing set, or other similar equations that can be conceived of by persons skilled in the art.

In some embodiments, the HARQ-ACK feedback timing set may include one or multiple subsets. Each subset may include one or multiple HARQ-ACK feedback timing values. Each HARQ-ACK feedback timing value corresponds to a slot level offset between the slot where a PSSCH is received (e.g., received by the Rx UE or transmitted by the Tx UE) and a slot where the corresponding PSFCH carrying the HARQ-ACK feedback (e.g., one HARQ-ACK information bit) for the PSSCH is transmitted (e.g., transmitted by the Rx UE or received by the Tx UE) . In some embodiments, a subset may include an inapplicable HARQ-ACK feedback timing value (e.g., a negative value such as “-1” ) , which can be defined as indicating that the HARQ-ACK feedback is disabled. The HARQ-ACK enabling/disabling indicator (if any) in the SCI can thus be removed.

In some embodiments, an indicator (denoted as indicator #2) in the SCI may be used to indicate a specific subset from the one or multiple subsets in the HARQ-ACK feedback timing set. The number of bits of indicator #2 can be based on the number of subsets in the HARQ-ACK feedback timing set. In this way, the PSFCH transmission occasion (s) is determined based on indicator #2.

In some embodiments, the transmission times (e.g., the number of transmission opportunities or PSFCH transmission occasions) of the HARQ-ACK feedback for the PSSCH may be based on the number of HARQ-ACK feedback timing values in the subset indicated by indicator #2.

For example, when a subset including a single (applicable) HARQ-ACK feedback timing value is applied (i.e., being indicated by indicator #2) , it implies that the HARQ-ACK feedback for the PSSCH is to be transmitted in a slot indicated by the single HARQ-ACK feedback timing value and the HARQ-ACK feedback is transmitted only once. For example, when a subset including multiple (applicable) HARQ-ACK feedback timing values is applied (i.e., being indicated by indicator #2) , it implies that the HARQ-ACK feedback for the PSSCH is to be transmitted in multiple slots (e.g., in multiple PSFCH transmission occasions) . Each of the multiple slots is indicated by a respective HARQ-ACK feedback timing value in the subset.

For example, for a subset including multiple HARQ-ACK feedback timing values, the multiple PSFCH transmission occasions are indicated by the multiple HARQ-ACK feedback timing values and each HARQ-ACK feedback timing value is in reference to the slot where the PSSCH is received. Theoretically, the more HARQ-ACK feedback timing values in a subset, the more transmission opportunities for the HARQ-ACK feedback, and the higher the reliability of the HARQ-ACK feedback.

For example, it is assumed that that the HARQ-ACK feedback timing set is configured as { {+2} , {+3} , {+4} , {+5} , {+6} , {+2, +4} , {+3, +5} , {+4, +6} , {+5, +7} , {+6, +8} , {+2, +4, +6} , {+3, +5, +7} , {+4, +5, +8} , {+2, +4, +6, +8} , {-1} } . According to the above embodiments, the HARQ-ACK feedback timing “-1” means that the HARQ-ACK feedback is disabled and other values indicate a slot level offset between the slot where a PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted.

For example, referring to FIG. 3, a UE may receive a PSSCH in slot n. In the case that indicator #2 of the SCI scheduling the PSSCH indicates the subset {+2, +4, +6, +8} from the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH can have a maximum of 4 transmission opportunities in slots n+2, n+4, n+6 and n+8 as shown in FIG. 3.

In the case that indicator #2 of the SCI scheduling the PSSCH indicates a subset with a single value (e.g., subset {+2} ) , the HARQ-ACK feedback for the PSSCH can have a single transmission opportunity in, for example, slot n+2. In the case that indicator #2 of the SCI scheduling the PSSCH indicates the subset {-1} , the HARQ-ACK feedback for the PSSCH is disabled.

From the perspective of an Rx UE, it may receive an SCI and a PSSCH scheduled by the SCI. The Rx UE can determine one or more PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH based on indicator #2 in the SCI. Assuming that the PSSCH is received on an interlace (denoted as interlace #2) , the Rx UE can determine a PSFCH resource for each of the one or more PSFCH transmission occasions based on interlace #2 (e.g., from a PSFCH resource pool) , indicator #2 and the HARQ-ACK feedback timing set. The Rx UE may transmit a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on the determined PSFCH resource in a corresponding PSFCH transmission occasion of the one or more PSFCH transmission occasions in response to the LBT test for transmitting the PSFCH being successful. In some embodiments, in response to the Rx UE transmitting the PSFCH in one of the one or multiple PSFCH transmission occasions, the Rx UE may drop a subsequent PSFCH transmission occasion (s) of the one or multiple PSFCH transmission occasions.

From the perspective of the Tx UE, it may transmit the SCI and the PSSCH scheduled by the SCI. The Tx UE can determine the one or more PSFCH transmission occasions for transmitting, by the Rx UE, HARQ-ACK feedback corresponding to the PSSCH based on indicator #2 in the SCI. The Tx UE can determine a PSFCH resource for each of the one or more PSFCH transmission occasions based on interlace #2, indicator #2 and the HARQ-ACK feedback timing set. The Tx UE can detect the PSFCH in the determined PSFCH resources. For example, the Tx UE can receive the PSFCH in one of the one or multiple PSFCH transmission occasions and may ignore the subsequent transmission opportunities of the PSFCH.

In some embodiments, the PSFCH resource may be determined based on the interlace where the PSSCH is received (e.g., interlace #2) , the HARQ-ACK feedback timing set (e.g., the number of subsets in the set) , and the values in the indicated subset associated with the PSSCH (e.g., indicator #2) .

For example, it is assumed that there are a total of M interlaces on the channel in the frequency domain. In some examples, the M interlaces can be indexed from 0 to M-1. A PSFCH resource pool may be defined considering the interlace resources and CS pair resources and include Y PSFCH resources. Each PSFCH resource in the pool may have an associated resource index within the PSFCH resource pool.

It is assumed that there are N1 subsets with applicable HARQ-ACK feedback timing values (i.e., non-negative integer values) in the HARQ-ACK feedback timing set. Denoting a subset including k₀, k₁, …, k_Z-1 being indicated by indicator #2 in the SCI (Z is the number of values in the indicated subset) and m the interlace index among the M interlaces (0<=m<=M-1) , for a given PSSCH transmitted on interlace m in slot n, (or m denotes the index of a predefined interlace among multiple interlaces (e.g., the lowest interlace index) for a given PSSCH transmitted on the multiple interlaces) , the corresponding PSFCH resource index can be expressed below as one example:

where i=0, 1, 2, …, Z-1, k_min denotes the minimum applicable value in the HARQ-ACK feedback timing set anddenotes the PSFCH resource index within the PSFCH resource pool pointing to the corresponding PSFCH resource for the (i+1) ^th transmission opportunities of the HARQ-ACK feedback. The PSFCH resource allocation starts in an ascending order of k and continues in an ascending order of m. The PSFCH resource mapping for a PSSCH is in an order of time first and frequency (interlace) second manner.

In some embodiments, the HARQ-ACK feedback timing set may include one or multiple subsets. Each subset may include one or multiple HARQ-ACK feedback timing values. In some examples, one (e.g., the first value) of the one or multiple HARQ-ACK feedback timing values in a subset may correspond to a slot level offset between the slot where a PSSCH is received (e.g., received by the Rx UE or transmitted by the Tx UE) and a slot where the corresponding PSFCH carrying the HARQ-ACK feedback (e.g., one HARQ-ACK information bit) for the PSSCH is transmitted (e.g., transmitted by the Rx UE or received by the Tx UE) . The remaining values (if any) of the one or multiple HARQ-ACK feedback timing values in the subset may correspond to a slot level offset between the slot where a previous PSFCH carrying the HARQ-ACK information bit for the PSSCH is transmitted and the slot where the corresponding PSFCH is transmitted, that is, a slot level offset between an associated PSFCH transmission occasion and its preceding PSFCH transmission occasion.

In some embodiments, a subset may include an inapplicable HARQ-ACK feedback timing value (e.g., a negative value such as “-1” ) , which can be defined as indicating that the HARQ-ACK feedback is disabled. The HARQ-ACK enabling/disabling indicator (if any) in the SCI can thus be removed.

In some embodiments, an indicator (denoted as indicator #3) in the SCI may be used to indicate a specific subset from the one or multiple subsets in the HARQ-ACK feedback timing set. The number of bits of indicator #3 can be based on the number of subsets in the HARQ-ACK feedback timing set. In this way, the PSFCH transmission occasion (s) is determined based on indicator #3.

In some embodiments, the transmission times (e.g., the number of transmission opportunities or PSFCH transmission occasions) of the HARQ-ACK feedback for the PSSCH may be based on the number of HARQ-ACK feedback timing values in the subset indicated by indicator #3.

For example, when a subset including a single (applicable) HARQ-ACK feedback timing value is applied (i.e., being indicated by indicator #3) , it implies that the HARQ-ACK feedback for the PSSCH is to be transmitted in a slot indicated by the single HARQ-ACK feedback timing value and the HARQ-ACK feedback is transmitted only once. For example, when a subset including multiple (applicable) HARQ-ACK feedback timing values is applied (i.e., being indicated by indicator #3) , it implies that the HARQ-ACK feedback for the PSSCH is to be transmitted in multiple slots (e.g., in multiple PSFCH transmission occasions) . For example, the number of transmission opportunities or PSFCH transmission occasions of the HARQ-ACK feedback is equal to the number of HARQ-ACK feedback timing values in the indicated subset. Each of the multiple slots is indicated by a respective HARQ-ACK feedback timing value in the subset. However, the reference slots may be different.

For example, for a subset including multiple HARQ-ACK feedback timing values (e.g., value #1, value #2, …, value #n, …) , value #1 is in reference to the slot where the PSSCH is received (i.e., indicating the slot level offset between the slot where the PSSCH is received and a slot of the first (earliest) PSFCH transmission occasion) , the remaining values (e.g., value #2 and value #n) are with reference to the slot where a previous PSFCH transmission occasion. For example, value #2 indicates the slot level offset between the first (earliest) PSFCH transmission occasion and the subsequent (second) PSFCH transmission occasion. For example, value #n indicates the slot level offset between the (n-1) ^th PSFCH transmission occasion and the subsequent (n^th) PSFCH transmission occasion.

Theoretically, the more HARQ-ACK feedback timing values in a subset, the more transmission opportunities for the HARQ-ACK feedback, and the higher the reliability of the HARQ-ACK feedback.

For example, it is assumed that that the HARQ-ACK feedback timing set is configured as { {+2} , {+4} , {+6} , {+8} , {+2, +2} , {+2, +2, +2} , {+2, +2, +2, +2} , {-1} } . According to the above embodiments, the HARQ-ACK feedback timing “-1” means that the HARQ-ACK feedback is disabled, the first value in a subset may indicate a slot level offset between the slot where a PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted, and each of the remaining values (if any) in the subset may indicate an offset between two associated adjacent PSFCH transmission occasions.

For example, referring to FIG. 4, a UE may receive a PSSCH in slot n. In the case that indicator #3 of the SCI scheduling the PSSCH indicates the subset {+2, +2, +2, +2} from the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH can have a maximum of 4 transmission opportunities in slots n+2, n+4, n+6 and n+8 as shown in FIG. 4. As will be described later, the UE may determine respective PSFCH resources (e.g., PSFCH resources 421-424) in these slots.

In the case that indicator #3 of the SCI scheduling the PSSCH indicates a subset with a single value (e.g., subset {+2} ) , the HARQ-ACK feedback for the PSSCH can have a single transmission opportunity in, for example, slot n+2. In the case that indicator #3 of the SCI scheduling the PSSCH indicates the subset {-1} , the HARQ-ACK feedback for the PSSCH is disabled.

From the perspective of an Rx UE, it may receive an SCI and a PSSCH scheduled by the SCI. The Rx UE can determine one or more PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH based on indicator #3 in the SCI. Assuming that the PSSCH is received on an interlace (denoted as interlace #3) , the Rx UE can determine a PSFCH resource for each of the one or more PSFCH transmission occasions based on interlace #3 (e.g., from a PSFCH resource pool) , indicator #3 and the HARQ-ACK feedback timing set. The Rx UE may transmit a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on the determined PSFCH resource in a corresponding PSFCH transmission occasion of the one or more PSFCH transmission occasions in response to the LBT test for transmitting the PSFCH being successful. In some embodiments, in response to the Rx UE transmitting the PSFCH in one of the one or multiple PSFCH transmission occasions, the Rx UE may drop a subsequent PSFCH transmission occasion (s) of the one or multiple PSFCH transmission occasions.

From the perspective of the Tx UE, it may transmit the SCI and the PSSCH scheduled by the SCI. The Tx UE can determine the one or more PSFCH transmission occasions for transmitting, by the Rx UE, HARQ-ACK feedback corresponding to the PSSCH based on indicator #3 in the SCI. The Tx UE can determine a PSFCH resource for each of the one or more PSFCH transmission occasions based on interlace #3, indicator #3 and the HARQ-ACK feedback timing set. The Tx UE can detect the PSFCH in the determined PSFCH resources. For example, the Tx UE can receive the PSFCH in one of the one or multiple PSFCH transmission occasions and may ignore the subsequent transmission opportunities of the PSFCH.

In some embodiments, the PSFCH resource may be determined based on the interlace where the PSSCH is received (e.g., interlace #3) , the HARQ-ACK feedback timing set (e.g., the number of subsets in the set) , and the values in the indicated subset associated with the PSSCH (e.g., indicator #3) .

For example, for each of the one or multiple PSFCH transmission occasions, a PSFCH resource corresponding to a PSFCH transmission occasion may be determined based on an index of interlace #3, values associated with the PSFCH transmission occasion and its preceding PSFCH transmission occasion (s) in the indicated subset, and the number of subsets of the plurality of subsets.

It is assumed that there are N2 subsets with applicable HARQ-ACK feedback timing values (i.e., non-negative integer values) in the HARQ-ACK feedback timing set. Denoting a subset including O₀, O₁, …, O_Z-1 being indicated by indicator #3 in the SCI (Z is the number of values in the indicated subset) and m the interlace index among the M interlaces (0<=m<=M-1) , for a given PSSCH transmitted on interlace m in slot n, (or m denotes the index of a predefined interlace among multiple interlaces (e.g., the lowest interlace index) for a given PSSCH transmitted on the multiple interlaces) , the corresponding PSFCH resource index can be expressed below as one example:

In some embodiments, the HARQ-ACK feedback timing set may include one or multiple subsets. Each subset may include one or multiple values.

In some embodiments, a subset may include at least one of the following: (A) a value indicating an offset between the slot where a PSSCH is received (e.g., received by the Rx UE or transmitted by the Tx UE) and a slot where the corresponding PSFCH carrying the HARQ-ACK feedback (e.g., one HARQ-ACK information bit) for the PSSCH is transmitted (e.g., transmitted by the Rx UE or received by the Tx UE) ; (B) HARQ-ACK feedback transmission times; or (C) a slot level offset between two adjacent PSFCH transmission occasions of one or multiple PSFCH transmission occasions for transmitting the HARQ-ACK feedback. The slot level offset between any two consecutive PSFCH transmission occasions is the same.

The number of transmission opportunities or PSFCH transmission occasions for transmitting the HARQ-ACK feedback may be based on parameter (B) . Theoretically, the more transmission opportunities or PSFCH transmission occasions for the HARQ-ACK feedback, the higher the reliability of the HARQ-ACK feedback.

For example, in some embodiments, when a subset does not include parameter (B) , it may suggest that the HARQ-ACK feedback is transmitted only once. That is, the number of PSFCH transmission occasions for transmitting the HARQ-ACK feedback is equal to 1. When a subset includes parameter (B) , the number of the PSFCH transmission occasions for transmitting the HARQ-ACK feedback is equal to the value of parameter (B) . In some embodiments, parameter (B) may not be included in any subset. For example, parameter (B) may be configured by a BS, by a Tx UE for an Rx UE, or by an Rx UE for a Tx UE, or may be predefined in standards or preconfigured.

In some embodiments, parameter (C) may not be included in a subset. Instead, parameter (C) may be configured by a BS, by a Tx UE for an Rx UE, or by an Rx UE for a Tx UE, or may be predefined in standards or preconfigured.

In some embodiments, a subset may include an inapplicable value (e.g., a negative value such as “-1” ) , which can be defined as indicating that the HARQ-ACK feedback is disabled. The HARQ-ACK enabling/disabling indicator (if any) in the SCI can thus be removed.

In some embodiments, an indicator (denoted as indicator #4) in the SCI may be used to indicate a specific subset from the one or multiple subsets in the HARQ-ACK feedback timing set. The number of bits of indicator #4 can be based on the number of subsets in the HARQ-ACK feedback timing set. In this way, the PSFCH transmission occasion (s) is determined based on indicator #4.

For example, it is assumed that that the HARQ-ACK feedback timing set is configured as { {+2} , {+4} , {+6} , {+8} , {+2, 2} , {+2, 3} , {+2, 4} , {-1} } and the parameter (C) (i.e., the slot level offset between two consecutive PSFCH transmission occasions) is configured as 2. According to the above embodiments, the value “-1” in the HARQ-ACK feedback timing set means that the HARQ-ACK feedback is disabled, and the first value (e.g., non-negative value) in a subset of the above HARQ-ACK feedback timing set may indicate the slot level offset between the slot where a PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted. The second value (if any) in the subset may indicate the HARQ-ACK feedback transmission times. According to some embodiments of the above embodiments, when a subset only includes one applicable value, it suggests a single transmission opportunity.

For example, referring to FIG. 4, a UE may receive a PSSCH in slot n. In the case that indicator #4 of the SCI scheduling the PSSCH indicates the subset {+2, 4} from the HARQ-ACK feedback timing set, the HARQ-ACK feedback for the PSSCH can have a maximum of 4 transmission opportunities in slots n+2, n+4, n+6 and n+8 as shown in FIG. 4. As will be described later, the UE may determine respective PSFCH resources in these slots.

In the case that indicator #4 of the SCI scheduling the PSSCH indicates a subset with a single value (e.g., subset {+2} ) , the HARQ-ACK feedback for the PSSCH can have a single transmission opportunity in, for example, slot n+2. In the case that indicator #4 of the SCI scheduling the PSSCH indicates the subset {-1} , the HARQ-ACK feedback for the PSSCH is disabled.

For example, it is assumed that that the HARQ-ACK feedback timing set is configured as { {+2, 1} , {+4, 1} , {+6, 1} , {+8, 1} , {+2, 2} , {+2, 3} , {+2, 4} , {-1} } and the parameter (C) is configured as 2. According to the above embodiments, the value “-1” in the HARQ-ACK feedback timing set means that the HARQ-ACK feedback is disabled, the first value (e.g., non-negative value) in a subset of the above HARQ-ACK feedback timing set may indicate the slot level offset between the slot where a PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted, and the second value in the subset may indicate the HARQ-ACK feedback transmission times.

For example, it is assumed that a UE may receive a PSSCH in slot n. In the case that indicator #4 of the SCI scheduling the PSSCH indicates the subset {+2, 1} , the number of transmission opportunities of the HARQ-ACK feedback for the PSSCH is equal to the second value in the subset, i.e., 1. Therefore, the HARQ-ACK feedback for the PSSCH can have a single transmission opportunity in, for example, slot n+2. In the case that indicator #4 of the SCI scheduling the PSSCH indicates the subset {-1} , the HARQ-ACK feedback for the PSSCH is disabled.

From the perspective of an Rx UE, it may receive an SCI and a PSSCH scheduled by the SCI. The Rx UE can determine one or more PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH based on indicator #4 in the SCI. Assuming that the PSSCH is received on an interlace (denoted as interlace #4) , the Rx UE can determine a PSFCH resource for each of the one or more PSFCH transmission occasions based on interlace #4 (e.g., from a PSFCH resource pool) , indicator #4 and the HARQ-ACK feedback timing set. The Rx UE may transmit a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on the determined PSFCH resource in a corresponding PSFCH transmission occasion of the one or more PSFCH transmission occasions in response to the LBT test for transmitting the PSFCH being successful. In some embodiments, in response to the Rx UE transmitting the PSFCH in one of the one or multiple PSFCH transmission occasions, the Rx UE may drop a subsequent PSFCH transmission occasion (s) of the one or multiple PSFCH transmission occasions.

From the perspective of the Tx UE, it may transmit the SCI and the PSSCH scheduled by the SCI. The Tx UE can determine the one or more PSFCH transmission occasions for transmitting, by the Rx UE, HARQ-ACK feedback corresponding to the PSSCH based on indicator #4 in the SCI. The Tx UE can determine a PSFCH resource for each of the one or more PSFCH transmission occasions based on interlace #4, indicator #4 and the HARQ-ACK feedback timing set. The Tx UE can detect the PSFCH in the determined PSFCH resources. For example, the Tx UE can receive the PSFCH in one of the one or multiple PSFCH transmission occasions and may ignore the subsequent transmission opportunities of the PSFCH.

In some embodiments, the PSFCH resource may be determined based on the interlace where the PSSCH is received (e.g., interlace #4) , the HARQ-ACK feedback timing set (e.g., the number of subsets in the set) , and the values in the indicated subset associated with the PSSCH (e.g., indicator #4) .

For example, for each of the one or multiple PSFCH transmission occasions, a PSFCH resource corresponding to a PSFCH transmission occasion may be determined based on an index of interlace #4, parameter (A) , parameter (C) , and the number of subsets of the plurality of subsets.

It is assumed that there are N3 subsets with applicable values (i.e., non-negative integer values) in the HARQ-ACK feedback timing set. Denoting a subset including {k, Z} being indicated by indicator #4 in the SCI (k is parameter (A) and Z is parameter (B) ) and m the interlace index among the M interlaces (0<=m<=M-1) , for a given PSSCH transmitted on interlace m in slot n, (or m denotes the index of a predefined interlace among multiple interlaces (e.g., the lowest interlace index) for a given PSSCH transmitted on the multiple interlaces) , the corresponding PSFCH resource index can be expressed below as one example:

where i= 0, 1, 2, …, Z-1, L denotes the value of parameter (C) (i.e., the slot level offset between two consecutive PSFCH transmission occasions) , k_min denotes the minimum (applicable) HARQ-ACK feedback timing value (e.g., the minimum parameter (A) ) in the HARQ-ACK feedback timing set, anddenotes the PSFCH resource index within the PSFCH resource pool pointing to the corresponding PSFCH resource for the (i+1) ^th transmission opportunities. The PSFCH resource allocation starts in an ascending order of k and continues in an ascending order of m. The PSFCH resource mapping for a PSSCH is in an order of time first and frequency (interlace) second manner.

Alternatively, can be expressed as orwhere k_max denotes the maximum (applicable) HARQ-ACK feedback timing value (e.g., the maximum parameter (A) ) in the HARQ-ACK feedback timing set, or other similar equations that can be conceived of by persons skilled in the art.

FIG. 5 illustrates a flow chart of exemplary procedure 500 for sidelink communications in accordance with some embodiments of the present disclosure. Details described in all of the foregoing embodiments of the present disclosure are applicable for the embodiments shown in FIG. 5. In some examples, the procedure may be performed by a UE, for example, UE 110 in FIG. 1.

Referring to FIG. 5, in operation 511, a first UE (e.g., Rx UE) may receive, from a second UE (e.g., Tx UE) , an SCI for scheduling a PSSCH, wherein the SCI includes an indicator for determining one or multiple PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH. The indicator may be indicator #1, indicator #2, indicator #3 or indicator #4 as described above.

In operation 513, the first UE may receive, from the second UE, the PSSCH on an interlace (e.g., interlace m) . In operation 515, the first UE may determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions. The methods for determining the PSFCH resource as described above may apply here.

In operation 517, the first UE may transmit, to the second UE, a PSFCH (denoted as “first PSFCH” for clarity) carrying the HARQ-ACK feedback corresponding to the PSSCH on a PSFCH resource (denoted as “first PSFCH resource” for clarity) in a PSFCH transmission occasion (denoted as “first PSFCH transmission occasion” for clarity) of the one or multiple PSFCH transmission occasions in response to a channel access procedure for transmitting the first PSFCH being successful.

For example, in some embodiments of the present disclosure, the indicator indicates an offset value (denoted as “first offset value” for clarity) of a plurality of offset values from a HARQ-ACK feedback timing set. The first offset value indicates an offset between a slot where the PSSCH is received and a slot where the first PSFCH is transmitted.

For example, in some embodiments of the present disclosure, the indicator indicates a subset (denoted as “first subset” for clarity) of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, each of which indicates an offset between a slot where the PSSCH is received and a slot where a corresponding PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted.

For example, in some embodiments of the present disclosure, the indicator indicates a subset (denoted as “first subset” for clarity) of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, which includes an offset value (denoted as “second offset value” for clarity) indicating an offset between a slot where the PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted.

For example, in some embodiments of the present disclosure, the indicator indicates a subset (denoted as “first subset” for clarity) of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes an offset value (denoted as “third offset value” for clarity) indicating an offset between a slot where the PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted, or both the third offset value and HARQ-ACK feedback transmission times.

In some embodiments of the present disclosure, the first UE may drop a subsequent PSFCH transmission occasion (s) of the one or multiple PSFCH transmission occasions in response to transmitting the first PSFCH in the first PSFCH transmission occasion.

It should be appreciated by persons skilled in the art that the sequence of the operations in exemplary procedure 500 may be changed and some of the operations in exemplary procedure 500 may be eliminated or modified, without departing from the spirit and scope of the disclosure.

FIG. 6 illustrates a flow chart of exemplary procedure 600 for sidelink communications in accordance with some embodiments of the present disclosure. Details described in all of the foregoing embodiments of the present disclosure are applicable for the embodiments shown in FIG. 6. In some examples, the procedure may be performed by a UE, for example, UE 110 in FIG. 1.

Referring to FIG. 6, in operation 611, a second UE (e.g., Tx UE) may transmit, to a first UE (e.g., Rx UE) , an SCI for scheduling a PSSCH, wherein the SCI includes an indicator for the first UE to determine one or multiple PSFCH transmission occasions for transmitting HARQ-ACK feedback corresponding to the PSSCH. The indicator may be indicator #1, indicator #2, indicator #3 or indicator #4 as described above.

In operation 613, the second UE may transmit, to the first UE, the PSSCH on an interlace. In operation 615, the second UE may determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions. The methods for determining the PSFCH resource as described above may apply here.

In operation 617, the second UE may receive, from the first UE, a PSFCH (denoted as “first PSFCH” for clarity) carrying the HARQ-ACK feedback corresponding to the PSSCH on a PSFCH resource (denoted as “first PSFCH resource” for clarity) in a PSFCH transmission occasion (denoted as “first PSFCH transmission occasion” for clarity) of the one or multiple PSFCH transmission occasions.

For example, in some embodiments of the present disclosure, the indicator indicates a first offset value of a plurality of offset values from a HARQ-ACK feedback timing set. The first offset value indicates an offset between a slot where the PSSCH is transmitted and a slot where the first PSFCH is received.

For example, in some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, each of which indicates an offset between a slot where the PSSCH is transmitted and a slot where a corresponding PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is received.

For example, in some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes one or multiple offset values, which includes a second offset value indicating an offset between a slot where the PSSCH is transmitted and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is received.

For example, in some embodiments of the present disclosure, the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set. The first subset includes a third offset value indicating an offset between a slot where the PSSCH is transmitted and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is received, or both the third offset value and HARQ-ACK feedback transmission times.

It should be appreciated by persons skilled in the art that the sequence of the operations in exemplary procedure 600 may be changed and some of the operations in exemplary procedure 600 may be eliminated or modified, without departing from the spirit and scope of the disclosure.

FIG. 7 illustrates a block diagram of an exemplary apparatus 700 according to some embodiments of the present disclosure. As shown in FIG. 7, the apparatus 700 may include at least one processor 706 and at least one transceiver 702 coupled to the processor 706. The apparatus 700 may be a UE or a BS.

Although in this figure, elements such as the at least one transceiver 702 and processor 706 are described in the singular, the plural is contemplated unless a limitation to the singular is explicitly stated. In some embodiments of the present application, the transceiver 702 may be divided into two devices, such as a receiving circuitry and a transmitting circuitry. In some embodiments of the present application, the apparatus 700 may further include an input device, a memory, and/or other components.

In some embodiments of the present application, the apparatus 700 may be a UE. The transceiver 702 and the processor 706 may interact with each other so as to perform the operations with respect to the UEs described in FIGS. 1-6.

In some embodiments of the present application, the apparatus 700 may further include at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may have stored thereon computer-executable instructions to cause the processor 706 to implement the method with respect to the UE as described above. For example, the computer-executable instructions, when executed, cause the processor 706 interacting with transceiver 702 to perform the operations with respect to the UEs described in FIGS. 1-6.

Those having ordinary skill in the art would understand that the operations or steps of a method described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of a method may reside as one or any combination or set of codes and/or instructions on a non-transitory computer-readable medium, which may be incorporated into a computer program product.

While this disclosure has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in other embodiments. Also, all of the elements of each figure are not necessary for the operation of the disclosed embodiments. For example, one of ordinary skill in the art of the disclosed embodiments would be enabled to make and use the teachings of the disclosure by simply employing the elements of the independent claims. Accordingly, embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure.

In this document, the terms "includes, " "including, " or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "a, " "an, " or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least a second or more. The term "having" and the like, as used herein, are defined as "including. " Expressions such as "A and/or B" or "at least one of A and B" may include any and all combinations of words enumerated along with the expression. For instance, the expression "A and/or B" or "at least one of A and B" may include A, B, or both A and B. The wording "the first, " "the second" or the like is only used to clearly illustrate the embodiments of the present application, but is not used to limit the substance of the present application.

Claims

A first user equipment (UE) , comprising:

a transceiver; and

a processor coupled to the transceiver, wherein the processor is configured to:

receive, from a second UE, sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH) , wherein the SCI comprises an indicator for determining one or multiple physical sidelink feedback channel (PSFCH) transmission occasions for transmitting hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback corresponding to the PSSCH;

receive, from the second UE, the PSSCH on an interlace;

determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and

transmit, to the second UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions in response to a channel access procedure for transmitting the first PSFCH being successful.
The first UE of Claim 1, wherein the indicator indicates a first offset value of a plurality of offset values from a HARQ-ACK feedback timing set; and

wherein the first offset value indicates an offset between a slot where the PSSCH is received to a slot where the first PSFCH is transmitted.
The first UE of Claim 2, wherein the first PSFCH resource is determined based on the index of the interlace, the first offset value, and a number of values in the plurality of offset values.
The first UE of Claim 1, wherein the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set; and

wherein the first subset comprises one or multiple offset values, each of which indicates an offset between a slot where the PSSCH is received and a slot where a corresponding PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted.
The first UE of Claim 4, wherein determining a PSFCH resource for each of the one or multiple PSFCH transmission occasions comprises: for each of the one or multiple PSFCH transmission occasions, determining a PSFCH resource based on the index of the interlace, a corresponding offset value in the first subset, and a number of subsets of the plurality of subsets.
The first UE of Claim 1, wherein the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set;

wherein the first subset comprises one or multiple offset values, which comprises a second offset value indicating an offset between a slot where the PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted; and

wherein each of the remaining offset values of the one or multiple offset values indicates a slot level offset between an associated PSFCH transmission occasion and its preceding PSFCH transmission occasion of the one or multiple PSFCH transmission occasions.
The first UE of Claim 6, wherein determining a PSFCH resource for each of the one or multiple PSFCH transmission occasions comprises: for each of the one or multiple PSFCH transmission occasions, determining a PSFCH resource based on the index of the interlace, offset values associated with a PSFCH transmission occasion and its preceding PSFCH transmission occasion (s) among the one or multiple offset values, and a number of subsets of the plurality of subsets.
The first UE of Claim 4 or 6, wherein a number of the one or multiple PSFCH transmission occasions is based on a number of offset values in the first subset.
The first UE of Claim 1, wherein the indicator indicates a first subset of a plurality of subsets from a HARQ-ACK feedback timing set; and

wherein the first subset comprises a third offset value indicating an offset between a slot where the PSSCH is received and a slot where a PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH is transmitted, or both the third offset value and HARQ-ACK feedback transmission times.
The first UE of Claim 9, wherein in the case that the first subset does not comprise the HARQ-ACK feedback transmission times, a number of the one or multiple PSFCH transmission occasions is equal to 1; or

in the case that the first subset comprises the HARQ-ACK feedback transmission times, the number of the one or multiple PSFCH transmission occasions is equal to the HARQ-ACK feedback transmission times.
The first UE of Claim 9, wherein the first subset further indicates a slot level offset between two adjacent PSFCH transmission occasions of the one or multiple PSFCH transmission occasions; or

wherein the slot level offset is configured by a base station (BS) or the second UE; or

wherein the slot level offset is predefined.
The first UE of Claim 11, wherein determining a PSFCH resource for each of the one or multiple PSFCH transmission occasions comprises: for each of the one or multiple PSFCH transmission occasions, determining a PSFCH resource based on the index of the interlace, the third offset value, the slot level offset and a number of subsets of the plurality of subsets.
The first UE of any of Claims 2, 4, 6, and 9, wherein the HARQ-ACK feedback timing set comprises an inapplicable offset value for disabling HARQ-ACK feedback for a PSSCH.
A second user equipment (UE) , comprising:

a transceiver; and

a processor coupled to the transceiver, wherein the processor is configured to:

transmit, to a first UE, sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH) , wherein the SCI comprises an indicator for the first UE to determine one or multiple physical sidelink feedback channel (PSFCH) transmission occasions for transmitting hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback corresponding to the PSSCH;

transmit, to the first UE, the PSSCH on an interlace;

determine, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and

receive, from the first UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions.
A method performed by a first user equipment (UE) , comprising:

receiving, from a second UE, sidelink control information (SCI) for scheduling a physical sidelink shared channel (PSSCH) , wherein the SCI comprises an indicator for determining one or multiple physical sidelink feedback channel (PSFCH) transmission occasions for transmitting hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback corresponding to the PSSCH;

receiving, from the second UE, the PSSCH on an interlace;

determining, based on an index of the interlace and the indicator, a PSFCH resource for each of the one or multiple PSFCH transmission occasions; and

transmitting, to the second UE, a first PSFCH carrying the HARQ-ACK feedback corresponding to the PSSCH on a first PSFCH resource in a first PSFCH transmission occasion of the one or multiple PSFCH transmission occasions in response to a channel access procedure for transmitting the first PSFCH being successful.